3 Answers
3

Condensation occurs when warm air meets a cold surface and when that air cools down, its ability to carry moisture reduces, so the water will distill and cling to the nearest surface (the same cold one).

As long as you don't detach the lens while the inside of your camera is colder, you should be fine. The little amount of air oozing through between lens and mount won't contain enough moisture to do harm.

You might also want to limit zooming actions to minimum - many lenses act as air pumps during zooming.

Using the camera, especially with live view or for capturing video, will heat up the sensor fairly fast. The rest of camera takes a bit longer to heat up, however; so ventilating its inside might still condensate some other important electronics, or the mirror.

Technically it can't form inside the sensor (which is just a silicon wafer with etched pathways), but can potentially form inside the sensor package.
Of course most people don't make that distinction :)

Sure, but it isn't as big a problem as to having it inside of your lens.

Condensation can occur anywhere there is a surface to attach to. With any electronic part condensation can lead to major issues. With the sensor depending on what else is around it may lead to dried spots on the sensor which would then should be cleaned.